udf: remove SLAB_MEM_SPREAD flag usage

The SLAB_MEM_SPREAD flag is already a no-op after removal of SLAB
allocator and in [1] it was fully deprecated. Remove its usage so we can
delete it from slab. No functional change.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/all/20240223-slab-cleanup-flags-v2-1-02f1753e8303@suse.cz/
Message-Id: <20240224135229.830356-1-chengming.zhou@linux.dev>